1. Technical Field
The present invention relates to a light emitting device and, more particularly, to a light emitting device including a semiconductor light emitting element.
2. Related Art
In Patent Document 1, a light emitting device is disclosed which includes a light emitting element, a mounting board for mounting the light emitting element thereon, a light transmission member for transmitting the light emitted from the light emitting element therethrough, a bonding member for fixedly bonding the light emitting element to the light transmission member, a light-reflective covering member for covering the side of the light transmission member and the light emitting element and a light-reflective frame provided on the mounting board and having the covering member filled therein. Here, the light transmission member is a plat-like body of a wavelength conversion member containing phosphors.
Patent Document 1: JP-A-2011-134829
In the technique disclosed in Patent Document 1, a primary light (blue light) is emitted from the light emitting element and a portion of the primary light is excited by the phosphors contained in the light transmission member (wavelength conversion member) to generate a wavelength-converted secondary light (yellow light). The primary light and the secondary light are mixed to generate a white light. The white light is emitted from the surface of the light transmission member, which is a light emitting surface of the light emitting device.
Here, the size of an external optical member (e.g., a reflector, a lens, etc.) having the light emitting device attached thereto can be reduced by reducing the area of the light emitting surface. Accordingly, it is required to reduce the area of the light transmission member that is a light emitting surface.
However, in the case where the area of the light transmission member is smaller than that of the upper surface of the light emitting element, the bonding member for fixedly bonding the light emitting element to the light transmission member sticks out from between the light emitting element and the light transmission member. Accordingly, there is a possibility that the whole peripheral end surface of the light transmission member is covered by the bonding member stuck out.
When the whole peripheral end surface of the light transmission member is covered by the bonding member, the primary light (blue light) of the light emitting element is transmitted through the bonding member and leaks to the outside of the light emitting device.
Then, the blue light emitted from the bonding member covering the whole peripheral end surface of the light transmission member is adversely noticeable against the white light emitted from the surface of the light transmission member. Accordingly, there is a problem that light emission quality is significantly reduced.
Accordingly, in the case where an amount of adhesive that is the bonding member is reduced in order to prevent the bonding member from sticking out from between the light emitting element and the light transmission member, there is a problem that a secure bonding fixation between the light emitting element and the light transmission member is hindered.
Further, a portion of the upper surface of the light emitting element is not covered by the light transmission member when the area of the light transmission member is smaller than that of the upper surface of the light emitting element. However, when the portion of the light emitting element is directly covered by a light-reflective covering member, the light emitted from the portion is blocked by the covering member, so that the light is not emitted to the outside from the light transmission member. Accordingly, there is a problem that the light extraction effect of the light emitting device is lowered.
The present invention has been made to solve the above-described problems and an object thereof is to provide a light emitting device where the light extraction effect can be improved, the area of a light emitting surface is small and the light emission quality is high.
The present inventors have intensively studied in order to solve the problems and reached each aspect of the present invention as described below.
<First Aspect>
A light emitting device includes a semiconductor light emitting element that is disposed on a surface of a board, a transparent phosphor plate that includes phosphors, a transparent bonding member that fixedly bonds an upper surface of the semiconductor light emitting element to a lower surface of the phosphor plate, and a reflective layer that surrounds the semiconductor light emitting element and the phosphor plate and contains light-reflective fine particles. The semiconductor light emitting element includes an exposed portion that is provided near an outer peripheral edge of the upper surface of the semiconductor light emitting element and is not covered by the phosphor plate but exposed. A portion of an outer peripheral end surface of the phosphor plate, which is located near the upper surface of the phosphor plate, is not covered by the bonding member. The exposed portion is covered by the reflective layer via the bonding member.
In the first aspect, a primary light is emitted from the semiconductor light emitting element and a portion of the primary light is excited by the phosphors contained in the phosphor plate to generate a wavelength-converted secondary light. The primary light and the secondary light are mixed to generate a mixed light. The mixed light is emitted from the surface of the phosphor plate, which is the light emitting surface of the light emitting device.
In the first aspect, the exposed portion which is not covered by the phosphor plate but exposed is provided near the outer peripheral edge of the upper surface of the semiconductor light emitting element. Accordingly, the area of the phosphor plate is smaller than that of the upper surface of the semiconductor light emitting element. As a result, it is possible to reduce the size of an external optical member (e.g., a reflector, a lens, etc.) having the light emitting device attached thereto.
Here, in the case where the area of the phosphor plate is smaller than that of the upper surface of the semiconductor light emitting element, the bonding member for fixedly bonding the semiconductor light emitting element to the phosphor plate sticks out from between the semiconductor light emitting element and the phosphor plate. Accordingly, there is a possibility that the whole peripheral end surface of the phosphor plate is covered by the bonding member stuck out.
When the whole peripheral end surface of the phosphor plate is covered by the bonding member, the primary light of the semiconductor light emitting element is transmitted through the bonding member and leaks to the outside of the light emitting device.
Then, the primary light emitted from the bonding member covering the whole peripheral end surface of the phosphor plate is adversely noticeable against the light emitted from the surface of the phosphor plate. Accordingly, there is a problem that light emission quality is significantly reduced.
However, in the first aspect, the portion of the outer peripheral end surface of the phosphor plate, which is located near the upper surface of the phosphor plate, is not covered by the bonding member.
Specifically, upon fixedly bonding the upper surface of the semiconductor light emitting element to the lower surface of the phosphor plate by the bonding member, there is no possibility that the bonding member stuck out covers the whole outer peripheral end surface of the phosphor plate even when the bonding member sticks out from between the semiconductor light emitting element and the phosphor plate.
Therefore, according to the first aspect, it can be prevented that the primary light of the semiconductor light emitting element is transmitted through the bonding member and leaks to the outside of the light emitting device. As a result, it is possible to provide the light emitting device where the light emission quality is high.
Further, in the first aspect, the portion of the outer peripheral end surface of the phosphor plate, other than the vicinity of the upper surface of the phosphor plate, is covered by the bonding member and the outer peripheral end surface of the phosphor plate is fixedly bonded to the semiconductor light emitting element via the bonding member covering the portion. Accordingly, it is possible to achieve a stronger bonding fixation, as compared to a case where only the upper surface of the semiconductor light emitting element and the lower surface of the phosphor plate are fixedly bonded to each other.
Meanwhile, the exposed portion which is not covered by the phosphor plate is provided in the upper surface of the semiconductor light emitting element when the area of the phosphor plate is smaller than that of the upper surface of the semiconductor light emitting element. However, when the exposed portion is directly covered by the reflective layer, the light emitted from the exposed portion is blocked by the reflective layer, so that the light is not emitted to the outside from the phosphor plate. Accordingly, there is a problem that the light extraction effect of the light emitting device is lowered.
However, in the first aspect, the exposed portion of the upper surface of the semiconductor light emitting element, which is not covered by the phosphor plate, is covered by the reflective layer via the bonding member, instead of being directly covered by the reflective layer.
Therefore, the light emitted from the exposed portion of the semiconductor light emitting element is transmitted through the bonding member covering the exposed portion, reflected at the reflective layer and then directed to the phosphor plate. In this way, the light is emitted to the outside from the phosphor plate, so that it is possible to improve the light extraction effect of the light emitting device.
<Second Aspect: Equivalent to First Embodiment and Second Embodiment>
In the light emitting device of the first aspect, an inclination portion is formed at the outer peripheral end surface of the phosphor plate, the inclination portion being connected to the lower surface of the phosphor plate at an obtuse angle and inclined in such a way that the area of the lower surface of the phosphor plate becomes smaller, and the bonding member includes a portion sandwiched between the upper surface of the semiconductor light emitting element and the lower surface of the phosphor plate, and a portion covering the exposed portion and the inclination portion.
In the second Aspect, the bonding member stuck out from between the semiconductor light emitting element and the phosphor plate forms the portion covering the exposed portion and the inclination portion by the surface tension thereof. The bonding member stuck out covers only the inclination portion. Accordingly, it is possible to reliably prevent the whole outer peripheral end surface of the phosphor plate from being covered by the bonding member stuck out.
Further, in the second aspect, the bonding member includes the portion covering the exposed portion and the inclination portion. Accordingly, the outer peripheral end surface of the phosphor plate is fixedly bonded to the semiconductor light emitting element via the portion of the bonding member. As a result, it is possible to reliably bond and fix the outer peripheral end surface of the phosphor plate to the semiconductor light emitting element.
Furthermore, in the second aspect, the light emitted from the exposed portion of the semiconductor light emitting element is transmitted through the portion of the bonding member, which covers the exposed portion and the inclination portion, reflected at the reflective layer and then directed to the phosphor plate. In this way, the light is emitted to the outside from the phosphor plate, so that it is possible to reliably improve the light extraction effect of the light emitting device.
Accordingly, according to the second aspect, it is possible to reliably obtain the operation/effect of the first aspect.
<Third Aspect: Equivalent to First Embodiment and Second Embodiment>
In the light emitting device of the second aspect, the inclination portion is formed only at the portion of the outer peripheral end surface of the phosphor plate, which is located near the lower surface of the phosphor plate.
In the third aspect, the bonding member stuck out from between the semiconductor light emitting element and the phosphor plate covers only the inclination portion. Accordingly, it can be reliably prevented that the portion near the upper surface of the outer peripheral end surface of the phosphor plate is covered by the bonding member stuck out. As a result, it is possible to reliably obtain the operation/effect of the second aspect.
<Fourth Aspect: Equivalent to Third Embodiment and Fourth Embodiment>
In the light emitting device of the first aspect, an undercut portion is formed at the outer peripheral end surface of the phosphor plate and has a shape that is obtained by cutting out a lower side of the phosphor plate, and the bonding member includes a portion sandwiched between the upper surface of the semiconductor light emitting element and the lower surface of the phosphor plate, and a portion covering the exposed portion and the undercut portion.
In the fourth aspect, the bonding member stuck out from between the semiconductor light emitting element and the phosphor plate forms the portion covering the exposed portion and the undercut portion by the surface tension thereof. The bonding member stuck out covers only the undercut portion. Accordingly, it is possible to reliably prevent the whole outer peripheral end surface of the phosphor plate from being covered by the bonding member stuck out.
Further, in the fourth aspect, the bonding member includes the portion covering the exposed portion and the undercut portion. Accordingly, the outer peripheral end surface of the phosphor plate is fixedly bonded to the semiconductor light emitting element via the portion of the bonding member. As a result, it is possible to reliably bond and fix the outer peripheral end surface of the phosphor plate to the semiconductor light emitting element.
Furthermore, in the fourth aspect, the light emitted from the exposed portion of the semiconductor light emitting element is transmitted through the portion of the bonding member, which covers the exposed portion and the undercut portion, reflected at the reflective layer and then directed to the phosphor plate. In this way, the light is emitted to the outside from the phosphor plate, so that it is possible to reliably improve the light extraction effect of the light emitting device.
Accordingly, according to the fourth aspect, it is possible to reliably obtain the operation/effect of the first aspect.
<Fifth Aspect: Equivalent to Third Embodiment and Fourth Embodiment>
In the light emitting device of the fourth aspect, the undercut portion is formed only at the portion of the outer peripheral end surface of the phosphor plate, which is located near the lower surface of the phosphor plate.
In the fifth aspect, the bonding member stuck out from between the semiconductor light emitting element and the phosphor plate covers only the undercut portion. Accordingly, it can be reliably prevented that the portion near the upper surface of the outer peripheral end surface of the phosphor plate is covered by the bonding member stuck out. As a result, it is possible to reliably obtain the operation/effect of the fourth aspect.
<Sixth Aspect: Equivalent to Fifth Embodiment>
In the light emitting device of the first aspect, an uppercut portion is formed at the outer peripheral end surface of the phosphor plate and has a shape that is obtained by cutting out an upper side of the phosphor plate, and the bonding member includes a portion sandwiched between the upper surface of the semiconductor light emitting element and the lower surface of the phosphor plate, and a portion covering only the exposed portion and a lower side of the uppercut portion.
In the sixth aspect, the bonding member stuck out from between the semiconductor light emitting element and the phosphor plate forms the portion covering only the exposed portion and the lower side of the uppercut portion by the surface tension thereof. The bonding member stuck out covers only the lower side of the uppercut portion. Accordingly, it is possible to reliably prevent the whole outer peripheral end surface of the phosphor plate from being covered by the bonding member stuck out.
Further, in the sixth aspect, the bonding member includes the portion covering only the exposed portion and the lower side of the uppercut portion. Accordingly, the outer peripheral end surface of the phosphor plate is fixedly bonded to the semiconductor light emitting element via the portion of the bonding member. As a result, it is possible to reliably bond and fix the outer peripheral end surface of the phosphor plate to the semiconductor light emitting element.
Furthermore, in the sixth aspect, the light emitted from the exposed portion of the semiconductor light emitting element is transmitted through the portion of the bonding member, which covers only the exposed portion and the lower side of the uppercut portion, reflected at the reflective layer and then directed to the phosphor plate. In this way, the light is emitted to the outside from the phosphor plate, so that it is possible to reliably improve the light extraction effect of the light emitting device.
Accordingly, according to the sixth aspect, it is possible to reliably obtain the operation/effect of the first aspect.
<Seventh Aspect: Equivalent to Fifth Embodiment>
In the light emitting device of the sixth aspect, the uppercut portion is formed only at the portion of the outer peripheral end surface of the phosphor plate, which is located near the upper surface of the phosphor plate.
In the seventh aspect, the bonding member stuck out from between the semiconductor light emitting element and the phosphor plate covers only the lower side of the uppercut portion. Accordingly, it can be reliably prevented that the portion near the upper surface of the outer peripheral end surface of the phosphor plate is covered by the bonding member stuck out. As a result, it is possible to reliably obtain the operation/effect of the sixth aspect.
<Eighth Aspect: Equivalent to First Embodiment>
In the light emitting device of any one of the first to seventh aspects, a plurality of semiconductor light emitting elements is arranged with gaps therebetween, and the phosphor plate is separately provided for each of the plurality of the semiconductor light emitting elements.
In the eighth aspect, the area of the phosphor plate is smaller than that of the upper surface of the semiconductor light emitting element and therefore intervals between respective phosphor plates can be widened. Accordingly, upon mounting the phosphor plate using a chip mounter, it can be prevented that the phosphor plate previously mounted is interfered with the phosphor plate later mounted. As a result, it is possible to easily produce the light emitting device.
<Ninth Aspect: Equivalent to Fourth Embodiment>
In the light emitting device of any one of the first to seventh aspects, a plurality of semiconductor light emitting elements is arranged with gaps therebetween, only one phosphor plate is provided for the plurality of the semiconductor light emitting elements, a recessed portion is formed at the lower surface of the phosphor plate and disposed so as to cover the gaps, and the bonding member includes a portion sandwiched between the upper surfaces of the semiconductor light emitting elements and the lower surface of the phosphor plate, and a portion covering the exposed portion and a portion of the recessed portion.
In the ninth aspect, the bonding member stuck out from between the semiconductor light emitting element and the phosphor plate forms the portion covering the exposed portion and a portion of the recessed portion by the surface tension thereof. Accordingly, it is possible to reliably prevent the whole outer peripheral end surface of the phosphor plate from being covered by the bonding member stuck out.
Further, in the ninth aspect, the bonding member includes the portion covering the exposed portion and a portion of the recessed portion. Accordingly, the outer peripheral end surface of the phosphor plate is fixedly bonded to the semiconductor light emitting element via the portion of the bonding member. As a result, it is possible to reliably bond and fix the outer peripheral end surface of the phosphor plate to the semiconductor light emitting element.
Accordingly, according to the ninth aspect, it is possible to reliably obtain the operation/effect of the first to seventh aspects.